Time....
And working on your sobriety.
Friendships get tested and difficult decisions like the one you made can have impacts that take time to work through. If he is your friend, chances are he's not NOT your friend because you made this difficult choice.
Let it sit for a while. If you were honest about why you made the call you did, then he knows what's going on for you whether he understands it or not. At some point, maybe a follow up - in person or via a call or letter - would help. Maybe invite him out for a lunch or dinner on you. Tell him you feel really badly and you want to celebrate his birthday with him, help him understand what led you to this really tough choice.
But, for the time being I'd say if he's 40 years old, he is a grown-aS*S* adult and should be mature enough to recognize that sometimes people have to take care of themselves. Addiction is serious business. It's life or death stuff. He may not fully appreciate the depth of your situation. Maybe you'll need to be vulnerable enough to be totally honest with him. Maybe you'll need to do some more explaining to help him see that your decision was not made with disrespect or lack of love, but out of protection for your very life.
If he doesn't see that at some point, well... maybe you'll need to part ways with that cat for a time. Because honestly, sobriety is about doing whatever it takes to save your own damn skin.
PS - You made the right choice.
